The present invention is generally related to sensing methods and systems. The present invention is also related to sensors and detectors utilized in security screening operations, such as those found at airports and other transportation centers. The present invention is specifically related to RF energy scanning and imaging methods and systems.
In light of the increasing threat of terrorism, a greater need for concealed weapon detection methods and systems for use at security checkpoints, such as those located at airports and other transportation hubs, is urgently needed. Conventional security systems include devices such as metal detectors and X-ray systems. Metal detectors can only detect metal objects such as knives and handguns. In addition, such devices cannot discriminate between innocuous items such as glasses, belt buckles, keys, and so forth, and are essentially useless in detecting modem threats posed by plastics, ceramic handguns, knives and even more dangerous items such as plastic and liquid explosives.
In order for sensors to detect concealed munitions beneath clothing, such devices must operate at frequencies that penetrate clothing barriers. This can be achieved by X-ray imaging. Although very effective for certain security tasks, X-ray imaging poses a serious health risk due to X-ray exposure and is therefore unacceptable to the public. Moreover, X-ray systems are not capable of remote imaging, which is rapidly emerging as a necessity in such security screening applications.
The present inventors believe that RF energy in the millimeter-wave (e.g., 30 GHz to 300 GHz) range, which can easily penetrate clothing, offers a possible solution for concealed weapon detection and imaging. Moreover, the present inventors believe that millimeter wave imaging systems can be either totally passive (non-radiating), or operate at very low power levels which poses no known threat to humans.
Current millimeter-wave imaging systems (e.g. Millivision""s hand-held scanner) operate in the 94 GHz band, providing a limited resolution to allow distinction between innocuous items and real threats, and lacks remote imaging capabilities. These systems include the following techniques; focal-plane 2D array and the holography. The first technique can be passive or active and incorporates an array of detectors placed at the focal plane of a large lens system. The main advantages are possible real-time imaging, compact size, operating akin to an optical camera. Disadvantages, however, include low resolution, small aperture size and field of view (FOV) and high cost.
Holographic imaging techniques utilize a linear array of sequentially switched transmitter/receivers operating at a single frequency. This array can be scanned quickly over a large aperture to effectively illuminate a target and the collected coherent returned signal can then be recorded and mathematically reconstructed in a computer to form a focused image without the need of a lens. Advantages include high resolution, mathematical focusing at any depth, large FOV. The chief disadvantage is the short depth of focus and the long range imaging capability. The present inventors thus believe that none of the aforementioned techniques have demonstrated real time imaging and the possibility of high-resolution long-range imaging for use in effective security screening. The present inventors therefore propose an improved method and system for concealed weapon detection for use in security screening, which is described in greater detail herein.
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
It is, therefore, one aspect of the present invention to provide improved sensing methods and systems.
It is another aspect of the present invention to provide for improved sensors and detectors utilized in security screening operations, such as those found at airports and other transportation centers.
It is yet another aspect of the present invention to provide for improved RF energy scanning and imaging methods and systems.
It is still another aspect of the present invention to provide for improved methods and systems for concealed weapon detection.
The aforementioned aspects of the invention and other objectives and advantages can now be achieved as is now summarized. Imaging methods and systems for concealed weapon detection are disclosed herein. In the active mode, a target can be illuminated for concealed weapon detection utilizing an illumination module that includes at least one wide-band RF source and at least one wide-beam antenna. Signals reflected from the target as a result of illumination by the illumination module can then be detected utilizing a scanning module that includes at least one scanning antenna in association with at least one wide-band millimeter-wave receiver.
The scanning antenna and the millimeter-wave receiver together collect the one or more signals reflected from the target, which can then be further analyzed and imaged for improved detection of concealed weapons. In the passive mode the receiver with scanning antenna acts in a manner that is analogous to a highly sensitive radiometer. Data scanned from the target by the scanning module can then be processed and displayed for further analysis by security personnel. Such data generally includes information concerning objects of the target that represent potentially concealed weapons.
The imaging methods and systems described herein preferably operate at a unique frequency of 140 GHz and afford real time imaging capabilities, high resolution, large field-of-view (FOV) and long range imaging. The high frequency of operation results in a small antenna size and provides for a fine spatial resolution that is highly desirable for effective imaging, particularly in the context of security screening operations. In an active mode, a target is illuminated by wide-band RF source. A mechanically scanned antenna, together with a highly sensitive wide-band millimeter-wave receiver can collect and process the signals reflected from the target. In a passive mode, the receiver detects black-body radiation emanating from the target and possesses sufficient resolution to separate different objects. The received signals can then be processed via a computer and displayed on a display unit thereof.